Google Earth and KML - Part Two (GETECH)

In the previous post I introduced the topic of working with geographic data in the KML format. As mentioned there, KML is the native data format used by Google Earth (GE) and it is widely supported by both GPS devices and software. I won't attempt to cover all the gory details of working with and editing KML in this series of posts (resource links at the end), but there a few practical things I've learned about working with GPS data in the KML format that I want to share.

As a basis for this discussion I'm looking at two GPS tracks I recorded on a short Kayak trip on the Kayaderosseras Creek near Saratoga Springs. One was recorded using my trusty Garmin GPS and the other was recorded using the GPS receiver in my camera; a Canon Sx260. I'll discuss and compare the accuracy of the two tracks and touch on some other issues you might encounter while using GPS to collect geo-referenced data for use in your projects.

The first issue is evident in the screen shot below (Image 1). The red line represents the track captured by the GPS receiver in the camera. The purple line shows the route recorded by the Garmin. The obvious difference is that the purple line extends beyond the point where the red line stops. That's because the red line stops at the place where I put the kayak into the creek and later took it out (at the Spa State Park Canoe Launch Site on Driscoll Road). I paddled upstream for a mile or so and then floated back down. I had both GPS units turned on and both units recorded the path. The purple line continues because when I got back to the launch point I forgot to turn off the Garmin GPS. So it recorded a track for the short carry from the creek up to the parking area and for my drive home. That data is not useful so the first thing I want to do is remove it.

Image 1: Screen capture from Google Earth. The two lines (red and purple) are GPS tracks recorded simultaneously on Kayak trip on the Kayaderosseras Creek near Saratoga Springs (NY)

I could do that by editing the track directly in Google Earth. That would be easy but it would be extremely tedious. There are several mouse clicks required to delete a point and there are a lot of points to get rid of to clean up this problem. You can see this in image two. For this screen capture I turned off the display of the track recorded by the camera (the red line) and selected the purple track for editing This makes visible the points recorded by the GPS. Each recorded point is represented by a red dot in the image and as you can see, there are a lot of points in just this short section of the route from the creek to my house. To remove this part of the track by editing it in GE you'd click on each points, select Delete, confirm the deletion and repeat. Lots of repeats.

Image 2: Screen capture from Google Earth. With the display of the track recorded by the camera (the red line) off, the track represented by the purple line was selected for editing. This allows us to see the individual points recorded by the GPS receiver. 

A better alternative is to open the KML file containing the track in a text editor and remove the unwanted points from the file. Once you have the hang of it you can edit the data in the file very quickly. There are few steps involved in this process which goes something like this:

1. Export the track to a file. In Google Earth right click on the item in the Places pane, select Save Place As. Be sure to select KML from the format drop down so the file is saved in the KML format.
2. Open the file in a text editor or an XML editor (I use Notepad++; a free and open source editor that is popular with programmers). You may need to configure your editor to recognize that the KML file is an XML file. That should allow the editor display the contents with nice formatting.
3. In this case, removing the points I don't want comes down to removing all the points where the latitude is greater than the latitude of the put-in point. I'm in the northern hemisphere --so the latitude coordinates increase as you go north-- and all the points I want to keep are south of the put-in. Image three shows the map zoomed in on that location with the properties dialog for the point displayed. The properties dialog shows the latitude and longitude of the marker (and the location). This is how I got the latitude I will use as the basis for my edits; any point with a latitude greater than 43.034293 can be removed from the file. A potential complication is that that the coordinates in the KML file are stored using the decimal degree format. That's as you see it in the dialog seen in image three, but that representation is not the default for coordinates in Google Earth. The default is to represent coordinates in the Degree/Minute/Second format; like this: 43°02'03.4548" You can change the representation used by Google Earth using the Options dialog on the Tools menu.

Image 3: Screen capture from Google Earth. Viewing the properties of a marker added at the location of the start/end point of the trip. The properties dialog shows the coordinates of that point.

Once you have a KML file containing your track, and you have a way to identify the point(s) to remove (in this case, latitude > 43.034293) you can remove the unwanted points from the file. To do this you do need to know a little bit about the XML data format and how to edit data stored in XML, but there are many introductions to XML available on-line and I've included references at the end of this post. Also, if you've done any work with HTML this will all look familiar. XML data elements are placed inside of tag pairs and you must delete the entire tag pair or you wil break the formatting of the file (and GE will complain when you try to reload it). You'll also need to recognize how the coordinates are represented. An example from my file looks like this:

<gx:coord>-73.79277999999999 43.034036 102.52</gx:coord>

The coordinate of the location is represented by three values with a space placed between each value (it might be hard to see the space; -73.79277999999999<space>43.034036<space>102.52). The values are:

-73.79277999999999	longitude	a "west" longitude represented as a negative number
43.034336	latitude	a "north" latitude represented as a positive number
102.52	elevation	meters above sea level

As discussed in the previous section, I want to delete any point where the latitude is greater than 43.034293, so this point can be removed from the file. The points are stored in the file in order, so once you find the place break between what you want and what you want to remove you can select all the bad rows and remove them. If editing data in this way is familiar to you then this should get you started. If this is entirely new then you may need more help. Look at the references or ask a friend who knows about this stuff.

With unwanted data removed from your file there is one final step; opening the file in Google Earth so you can see the results of your work. In Google Earth select "Open" from the File menu and find your edited file on disk. If you get warnings about errors check the file over for mis-matched tag pairs. That's it, you can save the file in your Places folder so that Google Earth reopens it automatically or you can reopen the file when you need it in the future.

This post is already rather long so I'm going to cover the other topics I raised at the start in a separate "part two" posting.

Geyser Creek to the Kaydeross

Most visitors to Saratoga Spa State Park experience Geyser Creek by strolling to see the impressive travertine deposits along its' banks or as the lovely stream that flows through the Geyser Creek picnic area. Fed by deep springs, the creek's waters are cool and attractive on even the hottest summer days. From the picnic area a trail follows the stream to the bridge that carries the park East West Road over the creek. At that point Geyser Creek is 20 feet wide and it typically carries a good flow of water. Downstream from the bridge you can see that the the creek flows into a swampy area, but there is no hint that within a quarter of a mile the stream will have all but vanished into that swamp. Water does flow out the other side, but that flow is in the form of seeps and trickles that add to the Kaydeross at various points. Some maps show Geyser Creek as a continuous line from the bridge to the Kaydeross, but don't believe them. There is no single, reliable, channel.

For much of the year bushwhacking into this area is a daunting prospect. Two small ridges punctuate the marsh but most of the area between the Park East West road (on the north) and Northline Road (on the south) is relentlessly wet, muddy, overgrown and buggy. During times of high water it's an impassable quagmire. The few people who visit the area mostly do so from the Kaydeross Creek. I've written previously about floating this stretch of the Kaydeross and a determined explorer could leave the creek at any number of points. As the crow flies it's just over two miles from the Canoe Launch at Gray's Crossing (Northline Road) to the launch site on Driscoll Road. The creek, however, takes four miles to cover that distance and the elevation differential is less than 20 feet. This is a flat landscape.

But there is one time of year when it is possible to enter the area on foot. In the dead of winter you can readily cross the frozen muck and mire to get a closer look at the topography and forests if not the impressive variety of flora and fauna seen during the warm weather months. Figure One shows a scene looking across the Kaydeross during the blizzard of Feb. 8, 2015. It was snowing hard.

Figure One: The banks of the Kaydeross during the blizzard of Feb. 8, 2015. Snow was falling at a rate of 2 inches per hour adding to the already deep snow pack. 

Lest you think I'm being overly dramatic talking about the conditions as a "blizzard'. You can judge for yourself from this short video. Watch the video in full screen to get the full effect.

Figure two shows my route. The snow pack was deep and airy so I left the parking near the Rte 50 Park entrance with my show shoes on. I first followed the Wetlands Overlook trail and then an abandoned road to reach the closed (and capped) Park Landfill. From there another abandoned Park road leads southwest into the forest. After a short distance I left the old road (on the left) bearing south and downhill to the edge of the swamp. I followed a route I had worked out ahead of time across the marshes and a small ridge to the Kaydeross. This route was selected to allow me to stay on State land though it's a somewhat arbitrary point in the winter. The trip covered only three miles for the round trip but with the deep snow and harsh conditions it seemed further.

Figure Two: Route from Rte. 50 parking to the Kaydeross
Map Image from Google Earth

Figure Three was made from the Ecological Communities map in the Saratoga Spa State Park Master Plan. The map legend is shown separately in Figure Four. This map also shows the outline of the State Owned lands and my route is represented by the prominent red line.

Figure Three: Ecological Communities - Saratoga Spa State Park south of the park East West Road. The red line shows my route.
Map Image captured from the Park Master Plan

Figure Four: Ecological Communities Map Legend
Image captured from the Park Master Plan

The Ecological Communities map shows the area to be a matrix of wetland community types with forest and successional fields mixed in. This is a rich ecological mix with the oxbow lakes and vernal pools being especially noteworthy. A vernal pool is an area that is reliably wet each spring but also completely dry for at least part of the year. That means no fish will be present and no fish makes vernal pools an attractive breading habitat for amphibians. Two vernal pools are shown on the map but there are certainly more. One reason that wetland complexes like this are so interesting is that the conditions are highly variable and the lines between community types are constantly being redrawn.

The weather on this day was harsh so most birds and beasts were keeping a low profile, I did see White-Tail Deer and common winter birds; Crows, Juncos, Blue Jays, a Hairy Woodpecker and a Pileated Woodpecker. In warmer weather this area is particularly rich in bird life and it is a designated Bird Conservation area. This is as good a place for bird watching as can be found in northeastern New York.

And my destination for this hike was not selected at random. I knew that the remnants of an old dam can be seen about half way between Grey's Crossing and Driscoll Road. You can find the location in the maps above because my route ends there. But the distinctive 90 degree change of direction taken by the Kaydeross at that point makes it easy to spot on any map. The broken down spillway creates a rapids and, even in this very cold winter, that's enough to maintain a small area of open water (Figure Five). As I approached the edge of the creek two White-Tails dashed into the woods. The ice around the open water was covered with deer tracks and we might surmise that they come here to drink.

Figure Five shows the spot but the flat light and deep snow make it difficult to see the outline of the former structure. I wonder when the dam was in use and its' purpose. I have not found much in the way of specific information about the dam or this area in general. If you know more, or have sources for this information, please leave a comment.

Figure Five: Open water below the old dam on the Kaydeross.

My First TriCorder

It's not quite a tricorder, yet, at least not as I remember them from Star Trek. But the smartphone in my pocket is an amazing device and the "possible" is evolving and expanding at a fantastic rate. I'm convinced that the combination of GPS, sensors and recording technologies into common devices will change the way we learn about our world.

A few months ago I wrote about the accuracy of the four GPS capable devices I had access to. The results of those tests can be found here. Not surprisingly I found that my two hand-held GPS units were significantly more accurate than the smartphone I was using at that time. Especially when the GPS handhelds were given a minute to average out accuracy limiting discrepancies that are inherent in the global positioning system.

I recently upgraded my phone to a Google Nexus 5 - a top of the line Android-based smartphone. Informal tests of the GPS capabilities of this phone show it to be as good or better than my GPS handhelds. The phone consistently produces results that are accurate in the 3 to 5 meter range. That's the standard for uncorrected GPS and more accurate fixes require correction and averaging of some kind. Previous generations of smartphones did not generally apply these corrections but it appears that the newest ones do. In short, my new phone consistently out performs all the other GPS devices I've previously used including the dedicated GPS handhelds.

But it's really the full range of capabilities that the phone incorporates, and the potential for those capabilities to be integrated, that makes this so exciting and intriguing. Michael Goodchild wrote about the potential of "citizens as sensors" in 2007. He identified several roadblocks to the usefulness of citizen sensors that mostly come down to questions of reliability. For research purposes accuracy is important, but the ability to quantify the level of accuracy is essential. Smartphones can record the data you want to get as well as data that says how accurate the data should be. Several of the GPS apps for my phone show the accuracy of the fix in real time and you can watch the accuracy change in response to satellites going in and out of view.

This blog and the Hemlock Forest research project are coalescing around this idea of "citizen sensoring". It's also March 1st today so the end of this colder than average winter is in sight or, at least, that's the thought we keep in mind to retain our sanity. Spring IS coming and I need to prepare for the spring-time phase of my project field work.

Citizen Sensor resources include:
Academic Biology and its Discontents
Citizen Sensors Improve World Health
Smart Citizen Fab Lab <== open source sensor hardware
Smart Citizen KickStarter
More on open source sensor kits

Citizen Science Data Management Guide


This Post: Resources and References
Goodchild, M.F. (2007). "Citizens as sensors: the world of volunteered geography". GeoJournal 69 (4): 211–221. doi:10.1007/s10708-007-9111-y
GPS Accuracy Comparison (http://dataliterate.blogspot.com/2013/11/gps-accuracy.html)

Data: Bittersweet

You can't talk about invasive plant species in this part of New York State and not talk about Asiatic Bittersweet (AB). This vine is one of the most visible and damaging of the invasive species found in the Hemlock Forest. I know a little more about the specifics of this plant because about 10 years ago it appeared in my backyard. I've been battling it there ever since. I cut it off at the ground and I pull it out by the roots. I've fought AB to a draw in my yard but it is everywhere in the surrounding area; especially in a successional field near my house where it has pulled down several trees by the sheer weight of the vines. AB spreads both by the dispersal of seeds by birds (that eat the berries) and via rhizomes that spread out from every established vine. This plant is not going away anytime soon.

Image One: A dense cluster of Asiatic Bittersweet vines in the Hemlock Forest.

Asiatic Bittersweet is not a shy plant and even in a dense forest spotting the vine is easy. It wraps itself tightly around the trunks of trunks of trees and it will bridge from tree to tree in the canopy. But it is in the late fall and winter that AB really stands out. Mature plants produce large quantities of orange-red berries with yellow sheaths that are quite distinctive. The only plant you might confuse it with is its native cousin, American Bittersweet. Asiatic Bittersweet hybridizes with the native variety and by all accounts the hybrid is quickly replacing the native version everywhere that both species are present. Unfortunately, the hybrids appear to take on the negative characteristics of the invader. Namely, it's ability to produce a mass of vines that tend to strangle whatever it gets a hold of. The native variety is certainly not extinct, so before you take actions to control this plant be sure you know which one you are looking at. The plants are very similar in appearance with one easily spotted distinction. When berries are present, if the berries are found all along the vine it is Asiatic Bittersweet. The berries of the native variety appear only at the very ends of each vine.

AB will be one of the plants I focus on in studying the invasive species present in the Hemlock Forest. The general questions I've discussed in other posts certainly apply and, in the case of AB, there is the additional issue of why the non-native variety is so much more destructive than the native species. In the Hemlock Forest AB is found pretty much everywhere there is an opening in the canopy. There are several old fields in various stages of succession in the forest and AB is present in all of them. It is almost certainly present in other places in the forest as well and one of my first goals will be to map the full extent of its' presence. That data can be used in the future to learn more about how AB disperses. AB can also be used to study how community assemblages are changed by a well established and aggressive invasive species.

Map One: The purple polygons show areas where Asiatic Bittersweet is present in significant quantities. This highly aggressive vine is probably found in other parts of the forest but I have not yet specifically mapped its' presence.


References and Resources:
Asiatic Bittersweet (Wikipedia)
Mistaken Identity: Invasive Plants and their Native Look-alikes

The Project - The Effect of Invasive Plant Species on Native Ecological Communities

I'm interested in systems. That includes computer systems; hence my day job as a software developer. But beyond earning a living, I've long been interested in complex systems and how information is represented within those system. This may be where my fascination with ecosystems and ecological communities comes from. Of course, it's also true that I just like to tramp through forests, fields and swamps so maybe that's it.

Recently I've been thinking about how ecological communities adapt to rapid change. Ecological communities are defined by combinations of plants and animals found in a specific environmental context. The Hemlock Forest contains a half dozen or so different community types (see the NYS Natural Heritage Ecological Communities Site) with names like, "Hemlock-Hardwood Swamp" and "Appalachian Oak-Pine Forest". At the scale of an ecological community rapid change can result from events such as a fire or from someone digging a ditch to drain a wetland. Or it can unfold more slowly such as when an aggressive non-native species becomes established in an area altering the established mix of plants and animals. Rapid changes unfold on time scales that we can see; a day, a month, a few years. But even change that takes place over a decade or two is barely a smidgen of an instant in terms of geologic or evolutionary time scales. From the perspective of geologic time, humanity is altering the ecological systems on the earth at a pace that resembles a great natural cataclysm. Much like when that famous asteroid struck and killed the dinosaurs or when a super volcano explodes and alters the composition of the atmosphere. We are running a gigantic experiment on the earth's systems by rapidly altering ecosystems at every scale.

Ecologists study these sorts of things but the pace and scale of the changes taking place now far outpace their (our) capacity to understand what is happening. We have put into motion changes that will produce a range of effects that future generations will have to deal with and our children and grand-children will probably be forced to manage and repair natural systems in ways that we really can't imagine (did you grandparents imagine the world we live in today?). To do that they will need to know as much as possible about how these systems worked before we messed around with them. Information is the key and our technologies, the same ones that have the potential to be our undoing, might also save us. These days, anyone with motivation can add to the data that might really matter to those working on these problems in the future.

Of course, access to tools doesn't mean that acquiring useful data is simple or obvious. What data is valuable? How do you actually get it? How do you manage it? These are among the questions that motivated me to create this blog. I don't have all the answers but maybe I can add something that is part of the solution. Whatever you figure out, please share. Unlike most ecosystems I can adapt rapidly when a better idea comes along.

The Plan

I live in the northeastern United States where some of the most interesting ecological communities are the wetlands: swamps, marshes, fens, bogs and so on. The Hemlock Forest area contains several different wetland community types in close proximity to each other. Image One shows a flooded forest (more formally a Red Maple Hardwood Swamp). Image Two shows a Perched, Swamp White Oak, Swamp. It's a perched swamp (the defining environmental characteristic) dominated by the Swamp White Oak (species). Interestingly, this community type is considered to be rare in New York State. It's not that the individual species are rare --Swamp White Oaks are fairly common-- but the perched swamp environment has brought together an uncommon combination of species. Image three shows a third wetland type present in the Hemlock Forest; your basic Hemlock-Hardwood Swamp.

Image One: The Hemlock Forest includes several different types of wetlands. The area pictured is a Red-Maple Hardwood Swamp - often referred to as a flooded forest. The species mix present in this area has been altered by the rapid spread of non-native plants and shrubs and also by past attempts to drain the swamp.

Image Two: The Perched, Swamp White Oak, Swamp area. It is a perched swamp because the surface water is disconnected from the water table by a layer of impermeable clay. The characteristic species is the Swamp White Oak; The large tree on the left is a Swamp White Oak.

Image Three: The forest contains numerous small Hemlock-Hardwood Swamps. The trees in the foreground are Hemlocks and the entire forest area is named after the stand of old growth hemlocks present in the northern half of the preserve.

The varied ecological communities present in this 300 acre forest make it appealing as a place to learn more about how ecological communities adapt to the introduction of aggressive non-native species. I've focused on plants and shrubs because they are relatively easy to identify and the Hemlock Forest area has significant populations of several non-native shrubs and vines including:

• Asiatic Bittersweet (Image Four)
• Japanese Barberry
• Burning Bush
• Japanese Knotweed

Image Four: A tangle of Asiatic Bittersweet vines. This aggressive invader is present throughout the forest where ever there is a break in the canopy.

Other invasive plants, shrubs, and trees (and creatures of various types) are present but these four spread rapidly and alter the composition of existing native communities. This raises additional questions, including:

• Why are these species so successful? Not all introduced species out-compete natives species or spread so rapidly
• To what extent, and how quickly, do native species adapt to these newcomers?
• Do non-native species alter established patterns of succession within native community types?
• Are there effective control methods for these species? And, if the makeup of a community has been altered by the established presence of non-native species, what effects might come from "controlling" the invader(s)? In other words, can "controlling" the invading species make matters worse?

These are bread-and-butter questions for ecologists and these plants have been studied extensively. Still, answers to these questions commonly start with, "It's unclear" or "It depends...". It depends on which invasive you are talking about and it depends on which ecological community type has been invaded. Asiatic Bittersweet (AB) is present in the forest where ever there is a break in the canopy. It is found along the margins of wetland areas and in successional areas used in the past for agricultural. But what about isolated breaks in the canopy such in the small marsh located near the center of the forest? I have not yet spotted any AB there. That marsh does contain Japanese Barberry, and quite likely other non-native wetland invaders, but why no AB? Is there something about the ecology of the marsh or is it simply that AB had not yet spread to that location?

There are many unknowns around how native communities adapt to species that suddenly appear on the scene. And that is the basis for my assertion that anyone can do important research by capturing data about these communities. The key is the use of methods that preserve the meaning of the data for the long term.

My project is based on an assumption that well established non-native species are part of a new norm for these communities. In other words, we may need to define new communities that incorporate the presence of these species. With that as a starting point I want to know whether newly adapted communities will be more or less resilient in the face of future changes. And these questions go well beyond new plant species appearing in swamps that few people ever see. Ecological changes also alter the mix and behaviors of non-plant species including friendly insects such as ticks and mosquitos. I grew up running and playing and tramping through forests and fields and swamps and ticks were almost never seen. A word of warning that if you visit the Hemlock Forest area, you need to take precautions against the deer ticks (Brown Legged Ticks) that carry Lyme disease. These little critters are very common and very friendly. The paper referenced in this article proposes that greater bio-diversity reduces the spread of parasitic disease and we are reducing biodiversity at a pace and scale that has rarely occurred in the past (the deep past, millions of years).

This post is a lot longer than I had intended but there you have it; the what and why; next up, the how.

References and Resources
Landscape Ecology (Wikipedia)
Study Shows How Biodiversity can Protect Against Disease

Where is this place? The Hemlock Forest

Where is this place I've been calling the Hemlock Forest?. The map below should help. Open up Google Maps and view the Saratoga Springs (NY) area (terrain view is best). The park is a prominent feature south of the city.

Map from Google Maps. The Hemlock Forest area is the park area (darker green) on the right. The orange lines show the trails and the marker is at the location of the parking area.

Of particular interest to me are the ecological communities present within the park and surrounding areas and the 2009 Park Master Plan includes a map of Park's ecological communities (You can view it here). Overall, Spa State Park is more developed than many others, but it also incorporates forested areas and a number of significant wetlands including an unusual Perched, Swamp White Oak, swamp.

The designation of ecological communities is based on both the landscape and the plant and animal communities that are present. The New York State Natural Heritage Program (run by the Department of Environmental Conservation) maintains a list of the community types found in New York State and where examples of those communities can be found. It's worth noting, however, that the classification of ecological communities is far from cut-and-dried. That's not a criticism, both the program and the website are well done and, for me at least, fascinating. But these designations are open to some interpretation and the communities change over time. It may be that new community types will have to be defined as natural systems adapt to changes resulting from human activity.

The potential for undesirable change is raised as a concern throughout the Park master plan which calls out the presence of invasive species -primarily plants and insects- as a significant threat to the natural heritage of the park. Several aggressive invasive wetland plants are present in the Hemlock Forest area (as they are throughout the park) and these plants pose a threat to native ecological communities. Two highly aggressive non-native plants -Oriental Bittersweet and Japanese Barberry- are now the dominant plant species in several areas of the Hemlock Forest. I plan to map these locations as part of surveying the state of the forest. Japanese Knotweed, another highly aggressive invasive species, is present near the parking area and that's worth watching. Once Knotweed gets going it is incredibly difficult to control.

Additional resources and information that you might find to be helpful.
Saratoga Spa State Park Master Plan
Saratoga Spa State Park Master Plan Map
Saratoga Spa State Park Master Plan Ecological Communities Map

Mystery Lines: What are those lines seen in the satellite images?

I love to visually explore an area using Google Earth (or similar software) and then go off and match up what is actually present on the ground with what I could see on the computer. Google Earth provides easy access to high resolution images but, if you are willing to dig a little deeper, there are many other sources of spatially referenced data that can be analyzed to learn about areas we want to study.

But let's talk specifics. Looking at satellite images of the Hemlock Forest area I noticed that there are some odd looking parallel formations present in one area of the forest. You can just make them out in the image from Google Earth (Image One). What are they? What process created them?

Image One: The lines are seen in the center of the image running at a 45 degree angle from upper right to lower left. The straight line that runs from top to bottom is a stone wall. Source: Google Earth, Historic imagery from April 1997.

Viewed in Google Earth I couldn't see enough detail to come up with a plausible explanation for what the lines represent or how they were created. But, for locations in New York State, other options exist including the very high resolution orthoimagery available from the New York State GIS Clearinghouse (NYSCG). Orthoimagery is a fancy name for aerial photographs; pictures taken from airplanes using high resolution cameras and techniques that minimize distortion. When you take pictures of the earth from a satellite the distance between the satellite and the ground pretty much ensures that the camera is at a right angle to the ground. So there is little or no distortion of the image. When you take those same pictures from an airplane, if the camera is not perfectly parallel with the ground, the images are distorted.

The imagery available from the New York State GIS Clearinghouse (NYSCG) covers (nearly) all of New York State and is available to the public via the NYSGC website. The catch is that there are thousands of files and they are big files. And, once you find the right images, you need a way to view them. These images are geo-referenced meaning that using the right software you can view the images and they will line up correctly with other map-based data layers. The software you use is commonly referred to as GIS; an acronym for Geographic Information System. Loaded into a GIS these geo-referenced images can be analyzed using a variety of methods. They can also be used to provide a base layer on which you overlay other data. This is much like what you do when you view satellite imagery in Google Earth and then add points or lines or outlines (polygons) on top.

The Hemlock Forest orthoimagery (Images Two and Three) (viewed using Quantum GIS) reveals a lot more detail and those curious lines now take on a distinctly man-made look. Particularly telling is the track that comes in from the left and crosses the formation (Image Three). They look like tire tracks but when taking measurements in the GIS I found that the lines in main set are about 50 yards apart. That made me think that they might be ditches created using a tractor or bulldozer. It is also more apparent from the orthoimages that the formations are filled with water. The dark color seen in the formations is the same as the color of small ponds and streams present in nearby areas.

Image Two: The lines are in the center of the image running at roughly a 45 degree angle to the top of the image. The red lines represent the boundary of the State Park. The park boundary is a separate layer viewed on top of the images in the GIS. Source: New York State GIS Clearinghouse.

Image Three: Zooming in for a closer view the structures and the "track" coming in from the left have a distinctly man-made look. Source: New York State GIS Clearinghouse

Still, I had to wonder why someone would create ditches -about 50 yards apart- through the forest at this place. That left only one solution: field trip. From the Hemlock Trail parking area twenty minutes by trail and another half hour winding my way through the swampy forest brought me to the place pictured in Image Four. This, clearly, was one of the ditches seen in the orthoimagery and it was also immediately apparent that these are ditches that someone dug.

Image Four: The ground view of one of the water courses seen in the aerial photos. Filled with debris and leaf litter these were probably a few feet deep when created. The surrounding area is a swampy, nearly level. The entire area has very poor drainage. So it seems likely that someone dug these ditches to provide drainage for some type of agriculture.

The ditches are roughly 50 yards apart and run in straight lines through the forest for two to three hundred yards. What was not apparent from the aerial imagery is that the area where these ditches are found is very flat and very swampy. A few larger and older trees are present but most of the trees are roughly the same size (and age). Based on the size of the trees I estimated that this area was probably in use for some type of farming 50 years ago.

But something was still missing. The surrounding areas were all clearly used for agriculture in the past but this area is very wet and it is surrounded by swamps. My visit took place in late November and it had been generally dry, and even so, every depression in this area is filled with water. During wetter parts of the year this area would likely be flooded. The trees that are present are types that you find in a hardwood swamp or floodplain forest.

However, after poking around a bit more, a possible explanation appeared. One of my interests is in how invasive species compete against native species so I'm always on the lookout for invasive plants and trees. And I noticed the presence of a number of small, stunted, trees interspersed among the common species. Being late November, with the leaves down, I couldn't tell right away what those trees were. Then, one of them gave up its' secret, on a branch I spotted a small apple. The stunted trees are apples trees and now I could see that someone had tried to drain the area to create an orchard.

It appears that that plan did not work out very well. Apple trees prefer well drained soil and perhaps the farmer was unaware that this area is notable for lying over a layer of impermeable clay. Not too far away that clay, combined with the nearly flat topography, has produced a type of wetland known as a "perched" swamp. A perched swamp is a wetland where the water on the surface is not connected to the local water table but where the drainage is so poor that you get a swamp anyway. In most swamps the water level rises and falls along with the local water table but this is a place where the water doesn't drain through the soil and runoff is slow or non-existent. Creating an orchard here was never going to be easy. Which may be why we now have this wonderful little wild area to explore and enjoy.

Resources:
New York State GIS Clearinghouse Orthoimagery

A little Wild: The Hemlock Forest

Things are changing. The way people think is changing. The natural world around us is changing. Everything is changing. This has always been the case; change happens. But one thing is different now. We humans are altering the global environment at a pace and scale that from the perspective of geologic time looks a lot like the great natural cataclysms of the past. Think in terms of huge super volcanoes that shook entire continents or the asteroid that killed of the dinosaurs. We are the human asteroid. We are in effect running a giant experiment on how the earth reacts to change at scale and lots of data is coming in. Our instruments and satellites capture immense amounts of data every day. Leaving us with the questions: "what can we learn?" and "what should we do?". That's the context for this blog.

OK, setting that cheery opening aside, I'm planning to write about very specific places that I think are interesting. One of those places is a small (300 acres) forest that is part of Saratoga Spa State Park. I call it the Hemlock Forest though that name is completely made up. Before going any further, let's look at a map (Figures One and Two).

Figure One: The City of Saratoga Springs, New York and surrounding areas. The green outline represents the boundary of Saratoga Spa State Park. The Hemlock Forest is on the right wedged in between Rte. 9 and the I87 (the Northway). The park covers approximately 2800 acres and that includes a tree nursery two golf courses, a Hotel and an outdoor performing arts center that seats 20,000 people (SPAC).

Figure Two: The Hemlock Forest is outlined in red. This section of Saratoga Spa State Park covers about 300 acres. The forest is separated from the main body of the Park by Rte. 9 (on the left). The northern edge of the forest runs into the rapidly developing urban/'suburban fringe of the City of Saratoga Springs. The southern margin is mostly undeveloped with a connection to the Kaydeross Creek other nearby natural areas.  

There are several interesting things going on in this little bit of forest. One is the presence of wetlands of several different types including an uncommon "perched" swamp (perched referring to how the swamp interacts with the local water table). This particular wet area, though small, hosts an uncommon ecological community anchored by the presence of old growth Swamp White Oak trees. The forest also includes an old growth hemlock forest and good stands of American Beech trees that so far have held up against the Beech Bark Disease that has devastated Beech trees elsewhere. The State Park maintains a two mile long trail that loops through a 150 year old forest that includes hemlocks, White and Red Pines, and Oaks. The existing trails provides direct access to less than half of the total area though the un-trailed southern portion of the forest is hardly an untrammeled wilderness. The entire area is crisscrossed by stone walls, old farm and field tracks, and unofficial trails. Still, parts of the forest have a distinctly wild feel and the range of habitats present make this an important natural preserve.

I enjoy walking the area and capturing data that represents the "current state" of the ecological communities that are present there and that will be one of things I'll write about in this blog. This "Field guide to the Hemlock Forest" will also include information on technologies and methods that I use, and that anyone can use, to gather real data about places like this. I'm sure that some posts will start with something like "saw a  Barred Owl today", but my emphasis will be on acquiring and managing data that represents the ecological and environmental state for this area. My hope is that this data will be useful in the future. In particular, I'm interested in how invasive species interact with native communities and I'm hoping to capture a data set that can be used to learn more about how those interactions change over time.

When I was a kid I loved to read about the explorers and naturalists who traveled the world finding species not known to western science. Unless you are willing to spend a lot of time looking through a microscope it's unlikely that any new species will turn up in northeastern New York, but spotting the arrival of a species that has not been present in the past is a very real possibility. We have tools at our disposal that were unimaginable even 20 years ago. A smartphone with GPS, environmental sensors, and on-line identification guides doesn't match a tricorder quite yet, but that's where we are headed.

If you are reading this it might be because you live nearby and can visit these places. Or maybe you are interested in nature generally and my writing is not so bad as to ruin it for you. Or, maybe, and this is my hope, you want to do something like this where you live. I'll be writing about citizen science and how we can contribute data towards a better understanding of our world.

That's all well and good but you may get an inkling that the for me this is fun. The Forest is less than a mile from my house and I like to walk in the woods. I used to play golf but, to paraphrase Mark Twiain's famous quip, "that's a sure way to ruin a nice walk." There is a parking area with trail access on the northern edge of the forest (access is from Crescent Avenue). The trails are lightly used and I'm yet to see another person while wandering off trail. Much of the area is swampy so if you do go off trail you can expect wet feet. And I'm not worried that publicizing the area will bring in swarms of hikers. For much of the year the hemlock forest is well defended by armies of mosquitoes and ticks (beware: Lyme Disease, seriously I have captured many many Deer Ticks while walking in this area). For now the Hemlock forest is well protected.

Resources:
Saratoga Spa State Park Master Plan (pdf)
Saratoga Spa State Park Master Plan Map